Question

Four students were assigned a science project to find out the pollution levels of lakes in their surrounding. After analysing the quality of water samples, the BOD values were found as follows :
Which among the following water samples is highly polluted ?

• A. 0.16 mg/L
• B. 0.6 mg/L
• C. 0.06 mg/L
• D. 6 mg/L

Answer 1

The Correct Option is D

The correct answer is (D) : 6 mg/L.

Answer 2

The correct answer is: (D) 6 mg/L.

The Biological Oxygen Demand (BOD) is a critical parameter in assessing water quality. It measures the amount of oxygen required by microorganisms to break down organic material in the water. The higher the BOD value, the greater the amount of organic matter present in the water, which in turn indicates higher levels of pollution.

In general, a BOD value of less than 3 mg/L is considered to indicate clean water, while values between 3-5 mg/L suggest moderate pollution. A value greater than 5 mg/L, such as 6 mg/L in this case, signals highly polluted water, as it indicates that a significant amount of oxygen is being consumed by microorganisms to decompose the organic pollutants.

Thus, the sample with a BOD of 6 mg/L is highly polluted compared to the others, which suggests that it has a higher concentration of biodegradable organic matter.